1. Field of the Invention
The invention relates to a radio frequency (RF) equalizer, and more particularly, to an RF equalizer capable of compensating for unflatness of the output RF signal power.
2. Description of the Related Art
Due to mobile communications technology advancements in recent years, various communications services, such as voice call services, data transfer services, and video call services, etc., may be provided to users regardless of their locations. Most mobile communications systems are multiple access systems in which access and wireless network resources are allocated to multiple users. The multiple access technologies employed by the mobile communications systems include the Global System for Mobile communications (GSM) technology, the Code Division Multiple Access (CDMA) technology, the Wideband Code Division Multiple Access (WCDMA) technology, and the Long Term Evolution (LTE) technology, etc. In addition, a major enhancement of LTE technology is LTE Advanced technology.
In order to support multiple communications technologies (for example, the GSM, CDMA, WCDMA, LET . . . etc.) from a single mobile device, multi-mode mobile devices have become common. Since the operation bands are different for different communications technologies, the multi-mode mobile device must support a wide range of frequency bands so as to sufficiently cover all of the different communications technologies operation bands. For example, the multi-mode mobile device should support frequency bands from 0.7 GHz to 3 GHz.
However, due to some electronic characteristics of the electronic devices utilized in mobile devices, there may be some fluctuations in the output signal power of RF signals after being processed by the mobile devices, causing unflatness of the output RF signal power in operation bands. FIG. 1a shows an exemplary curve of output RF signal power versus frequency. In the example, the output RF signal power decreases as frequency increases. FIG. 1b shows another exemplary curve of output RF signal power versus frequency. In the example, the output RF signal power increases as frequency increases, where the increment or decrement in the signal power is a phenomenon of the unflatness of the output RF signal power.
In order to solve the unflatness of the output RF signal power, RF equalizers capable of compensating for unflatness of the output RF signal power are provided.